The U.S. Supreme Court has unanimously upheld the drawing of state electoral districts based on total population, not eligible voters, rejecting a conservative challenge in a Texas case that threatened the political influence of urban minority groups.

The challengers argued drawing local district maps based on total population, rather than eligible voters, undermines the power of rural areas and violates the "one person, one vote" rule requiring political districts to be roughly equal in population.

Texas is one of many states with densely populated urban areas that include large numbers of Latino and other immigrants, many of whom are not citizens or are too young to vote.

If their presence were ignored in district maps, it would have severely reduced the political power of minority groups that have voted overwhelmingly for the Democratic Party in recent elections.

FILE - Supreme Court Ruth Bader Ginsburg

Writing her opinion for the court, Justice Ruth Bader Ginsburg said "constitutional history, the court's decisions, and longstanding practice" all say states may draw legislative districts based on total population.

"Jurisdictions may design state and local legislative districts with equal total populations, we hold; they are not obliged to equalize voter populations," said Ginsburg.

The ruling does not affect U.S. Congressional districts, which are required to be based on total population.